search - what's the efficient algorithm to find points in a circle based on geographic coordinates? -


i'm working on implementation finding nearest person based on geographic coordinates. example, person a has coordinates（longitude , latitude ） m, , want find person within circle of center m radius x.

i plan store geographic coordinates in mysql database, what's efficient way search nearest coordinates?

my specific question is:

  1. what fields should stored in database efficient search? plan store persons' coordinates only.
  2. what's algorithm finding nearest person? plan calculate distance between person a's coordinate , coordinates stores in database.

however, think less efficient calculate if number of coordinates huge in database.

what's better way achieve application?

a simple pithagoras theorem application:

-- coordinates of person @ center of "circle" set @x0 = (select x persons id=1),     @y0 = (select y persons id=1); -- calculate distance each point in persons table, excluding "center" select *, sqrt(pow(x - @x0, 2) + pow(y - @y0, 2)) distance persons id != 1 order sqrt(pow(x - @x0, 2) + pow(y - @y0, 2))

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